From a pure performance standpoint, Auston Matthews has steadily fallen behind Nathan Mackinnon, Leon Draisaitl and Nikita Kucherov in the forward rankings over the past few years, and I don't he should based on the toolset he has to play the game. For me, he's simply made any of the long term behavioral changes and growth on the ice to consistently be where he has already demonstrated he can get occasionally. Play harder, use your body more efficiently, straighter lines, more mission focused.
While his goal scoring has been best in the business, he lags far behind in the Art Ross conversation and making those around him more productive compared to his peer group who has repeat years in the 110s-140s. That's in the regular season alone. We simply are paying him the most money in the game but aren't getting anything close to that kind of production.
That's before we even get to the problem that he's not a playoff performer. At all. Every 7 game series, he's good for 1 or 2 breakout games, but compare that to Mackinnon, Draisaitl, Kucherov, look at the kind of runs their teams are capable of going on with them leading the way. Like other top 5 guys, he can't sustain and the team goes nowhere year after year. All of this is heaped on Marner, but the share of blame should be a lot more equal.
From an injury perspective, we don't have any real information, so all this is in the land of speculation. But if you're throwing around "inept" as a word, I don't know one could look at the way Matthews and the Leafs have handled this as "competent."
If Matthew was hurt in the playoffs, the summer months were not used to make sure he was healthy going into this season. If he wasn't healthy in training camp, the time wasn't used to get him right in the regular season. And if it was so serious that he was off for a month and had to go to Germany for treatment, it didn't get him right again. So from what we've seen with ineffective treatment, poor play and 7 months of recurring injuries and performance related dips and massive state secrets, I'd say yeah maybe the team and player aren't handling this properly. But we have no information otherwise.
This whole project is not where it needs to be.